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The spectrum of the planetary nebula NGC 6572.
Feibelman, W. A.; Hyung, S.; Aller, L. H.
A detailed, high-spectral-resolution study of the spectrum of the planetary nebula NGC 6572 is made for the optical region 365 to 1005 nm, using the Hamilton echelle spectrograph of Lick Observatory, and for the ultraviolet (UV) spectral region 125 to 320 rIm with the high-dispersion mode of the International Ultraviolet Explorer (lUE) satellite. …
No fundamental-mode pulsation in R Leonis ?
Tuthill, P. G.; Feast, M. W.; Haniff, C. A. +1 more
We present new and precise angular diameter measurements of the long-period variable R Leonis at 833 and 903 nm. Our inferred photospheric diameter (38±2.5 mas) and stellar effective temperature (2459 + 150 K) are both in good agreement with recent determinations made at the same variability phase in the near-infrared. Assuming a parallax of 8.3 m…
Hubble Space Telescope observations of the BL Lac object PKS 1413+135 : the host galaxy revealed.
Abraham, R. G.; McHardy, I. M.; Crawford, C. S. +1 more
In an earlier paper, we showed that the BL Lac object PKS 1413 + 135 appears to lie in a disc-dominated galaxy with colours closer to those of an elliptical than a spiral galaxy. Subsequently, a large neutral hydrogen absorption feature was found at the optical redshift of the proposed host galaxy together with a substantial absorbing column in th…
RE 1738+665: the hottest DA white dwarf detected by ROSAT.
Barstow, M. A.; Koester, D.; Sansom, A. E. +6 more
One of the most important results of the ROSAT all-sky X-ray and EUV surveys has been the discovery of a large number of previously uncatalogued white dwarfs. One of these, RE 1738+665, is found to be the hottest hydrogen-rich DA white dwarf detected, with a temperature of 88000 K and log g =7.8, lying significantly above the 70000-K observational…
The nature of the newly discovered DO white dwarf RE 0503-289.
Werner, K.; Barstow, M. A.; Holberg, J. B. +2 more
We report the discovery of a hot DO white dwarf, RE 0503 - 289, which lies in a region of very low interstellar H I density. It lies within 1 deg of the hot DA white dwarf RE 0457 - 281 which we have reported as having the lowest directly measured H I column. A follow-up observation made using the Voyager 2 UV spectrometer reveals a strong continu…
ROSAT/XRT-PSPC observations and the ionizing continuum of Seyfert 1 galaxy MKN 478
Gondhalekar, P. M.; Kellett, B. J.; Matthews, L. +2 more
The ROSAT/XRT-PSPC observations of the Seyfert 1 galaxy Mrk 478 are presented. Together with the optical and ultraviolet spectra of this galaxy, obtained within 8 months of the X-ray observations, these new data are used to determine the continuum energy distribution (CED) of Mrk 478, from 1 micron to about 2.0 keV with a small break between 11.3 …
He II lines from cataclysmic variable winds.
Hoare, M. G.
We present the first quantitative examination of the contribution of the stellar winds in high accretion rate, non-magnetic cataclysmic variables to the He II λ1640 and λ4686 lines. The line profiles are simulated with the Sobolev approximation using level populations taken from previous NLTE calculations which matched the observed strengths of th…
Extreme-ultraviolet spectrophotometry of HD 15638 and HR 8210 (IK Peg).
Barstow, M. A.; Koester, D.; Holberg, J. B.
The main-sequence stars HR 8210 (1K Peg) and HD 15638 have both been found to have DA white dwarf companions by observations with the lUE satellite, following their discovery as bright EUV sources by the ROSA T Wide Field Camera. Accurate estimates of the temperature and surface gravity of each white dwarf, based on the lUE data, were oniy possibl…
A new hot DA white dwarf in a region of exceptionally low HI density.
Kepler, S. O.; Fontaine, G.; Barstow, M. A. +11 more
We report the discovery of the hot DA white dwarf RE 0457-281 which has the lowest line-of-sight neutral hydrogen column density yet measured. The star was found independently by the ROSAT EUV, Montreal-Cambridge-Tololo and Edinburgh-Cape surveys. With an effective temperature of 60700 K and very soft EUV spectrum, this white dwarf resembles the w…
Multifrequency monitoring of the Seyfert 1 galaxy NGC 4593 - I. Isolating the nuclear emission.
Glass, I. S.; Clavel, J.; Peterson, B. M. +4 more
We present data obtained within a Campaign to monitor spectral variations in the low-luminosity Seyfert 1 galaxy NGC 4593, at X-ray, ultraviolet, optical and near-IR (J, H, K and L) frequencies. The different `parasitic' contributions that contaminate the pure nuclear continuous emission have been isolated and modelled. The light from the composit…